Quarterly report pursuant to Section 13 or 15(d)

Investment Securities - Schedule of Amortized Cost and Estimated Fair Value of Investment Securities by Contractual Maturity (Detail)

v2.4.1.9
Investment Securities - Schedule of Amortized Cost and Estimated Fair Value of Investment Securities by Contractual Maturity (Detail) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Mar. 31, 2014
Summary of Investment Holdings [Line Items]      
Available-for-Sale Within one year, Amortized Cost $ 11,995us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost    
Available-for-Sale Over one year through five years, Amortized Cost 11,341us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost    
Available-for-Sale Over five years through ten years, Amortized Cost 88,960us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost    
Available-for-Sale Over ten years, Amortized Cost 64,253us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost    
Available-for-Sale, Amortized Cost 849,190us-gaap_AvailableForSaleSecuritiesAmortizedCost 1,061,703us-gaap_AvailableForSaleSecuritiesAmortizedCost  
Available-for-Sale Within one year, Estimated Fair Value 11,948us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue    
Available-for-Sale Over one year through five years, Estimated Fair Value 11,363us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue    
Available-for-Sale Over five years through ten years, Estimated Fair Value 89,001us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue    
Available-for-Sale Over ten years, Estimated Fair Value 63,935us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue    
Available-for-Sale, Estimated Fair Value 858,064us-gaap_AvailableForSaleSecurities 1,060,717us-gaap_AvailableForSaleSecurities 520,990us-gaap_AvailableForSaleSecurities
Collateralized mortgage obligations [Member]      
Summary of Investment Holdings [Line Items]      
Available-for-Sale, Amortized Cost 164,163us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_ShortTermDebtTypeAxis
= us-gaap_CollateralizedMortgageObligationsMember
188,704us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_ShortTermDebtTypeAxis
= us-gaap_CollateralizedMortgageObligationsMember
 
Available-for-Sale, Estimated Fair Value 165,405us-gaap_AvailableForSaleSecurities
/ us-gaap_ShortTermDebtTypeAxis
= us-gaap_CollateralizedMortgageObligationsMember
188,047us-gaap_AvailableForSaleSecurities
/ us-gaap_ShortTermDebtTypeAxis
= us-gaap_CollateralizedMortgageObligationsMember
 
Mortgage-backed securities [Member]      
Summary of Investment Holdings [Line Items]      
Available-for-Sale, Amortized Cost 485,112us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
571,678us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
 
Available-for-Sale, Estimated Fair Value 492,896us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
573,286us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
 
Other securities [Member]      
Summary of Investment Holdings [Line Items]      
Available-for-Sale, Amortized Cost 22,916us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_OtherDebtSecuritiesMember
22,916us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_OtherDebtSecuritiesMember
 
Available-for-Sale, Estimated Fair Value 23,100us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_OtherDebtSecuritiesMember
22,893us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_OtherDebtSecuritiesMember
 
Equity securities [Member]      
Summary of Investment Holdings [Line Items]      
Available-for-Sale, Amortized Cost 450us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
450us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
 
Available-for-Sale, Estimated Fair Value $ 416us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
$ 414us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember